#include <bits/stdc++.h>
#define ll long long
using namespace std;

int f[25][25], n;
//i表示还未入栈的， j表示栈中有的
int main()
{
  cin >> n;
  for(int i = 0; i <= n; i++){
  	for(int j = 0; j <= n; j++){
  		if(!i) f[i][j] = 1;
  		else if(!j) f[i][j] = f[i-1][1];
  		else f[i][j] = f[i-1][j+1] + f[i][j-1];
	  }
  }
  cout << f[n][0] << endl;
  return 0;
}	